Never trust the seller's inspection - not even mine. I know, I guarantee mine but let me tell you a little story about a small house that had a big problem.
I did not do the seller's inspection. I was working for the buyer in a house that was built in the later part of the 1920's. The listing agent had offered to sell the report that his client had to the my client but he, fortunately, wanted independent eyes. No problem.
Everything was tracking pretty normally for a house of that vintage until I got into the crawlspace. Skinny one and I couldn't get to the front half of the home due to the total lack of clearance. I'm skinny but even I wasn't getting there without a shovel - and I deliberately don't carry one on the truck. Same thing with hammers. They both encourage risky behavior in the inspector.
One tool that I do carry into the crawlspace is a 4" awl for probing wood. Even a sound piece of wood can harbor a surprise or two so testing is the best method of determining what's there. A rock hammer is also useful - sometimes you can hear the difference between sound wood and something that is riddled with pests.
In this case, I knew there was a problem reasonably quickly since white icky stuff (fungus of some sort, obviously) should not be eating the framing members. It's just bad form. Also, might not be too healthy to live around.
Fungus is usually going to grow in high humidity/moisture environments. Dry rot is actually wood-destroying fungus and doesn't happen when things are dry.
If you look at the picture, you can see the handle of the awl. Now, for those that don't know me, I'm not a power lifter. I'm a long distance runner with the arms of a long distance runner. The fact that I could embed that awl to the hilt was not good news. That the main beam dropped 2" because of rot was not good news.
What was really disturbing to me was the buyer was not apprised of these conditions in the disclosures. Which means that the other inspector thought the space was too tiny to get into and didn't try.
Fortunately, my client was a trust but verify kind of investor. Will the deal go forward? Don't know, that's not my part of the job. Mine is to give good, solid information. If the client hadn't retained me, he wouldn't have had the accurate data to make his decision.